Developing Global Consensus: IEEE Standard 1820 Guide on Selection of T&D Insulators
by William A. Chisholm

Insulators are selected to withstand a range of outdoor conditions, providing low probability of flashover, especially under normal operating voltage, during an expected long service life. There are some special considerations that affect the application of insulators in ‘cold weather conditions’, defined as ambient temperature < 0°C. Contamination can accumulate for months, ice can accrete on insulators and bridge the normal leakage distance, and frost can stabilize pollution during melting.